1. Field of the Invention
The present invention relates to an electronic printer that uses an electroluminescent display such as an organic-inorganic electroluminescent display panel.
2. Description of the Related Art
A color imaging technique known as the KNC process directly overlays color toner images on a photoconductive drum by repeatedly charging, exposing, and reverse developing the toner images on the photoconductive drum, and then batch transfers the overlaid toner images to a transfer medium in a single step.
A feature of this process is in the use of a subtractive color mixture for directly overlaying toner images on the photoconductive drum, thereby forming and developing one latent image on top of the previous image(s). Image exposure can be accomplished from either the inside or outside of the photoconductive drum.
A subtractive color mixture for overlaying the toner images is needed to form a color image.
The wavelength usable for image exposure is limited with external image exposure techniques because the toner image is already on the photoconductive drum. However, with methods in which the second image is exposed from inside the photoconductive drum (internal exposure), a latent image can be formed without being affected by light cover by the toner layer on the photoconductive drum. It is therefore only necessary to compensate for the toner layer potential, and color compensation is greatly reduced.
The photoconductor used in this internal exposure method is typically a drum and an LED head is typically used for the light source instead of laser optics because downsizing and positioning are easier. The drum diameter can be reduced 30% to 40% compared with an external exposure method. Positioning precision and toner image overlaying are also improved with internal development because the images are exposed from inside the drum by an LED unit disposed inside the transparent drum.
A compact, high speed color printer in which positioning precision and color image superimposition are improved in principle can thus be achieved with an internal development method combined with a compact LED head optical system.
While toner dispersion and image shifting are problems with image transfer techniques, these are reduced by single image transfer, which is thus suited to higher image quality and does not have the limitations imposed by a transfer medium. However, when an LED unit is used for the light source in an internal image exposure technique, it is necessary to gather light from the LED unit for primary scanning (axially to the drum). Furthermore, while positioning precision is improved compared with external image exposure, the write timing of each color image is dependent upon the precision of the rotational speed of the drum.
Furthermore, while there are methods whereby it is possible to eliminate primary scanning by using the LED unit as a line light source, LED alignment precision is relatively low at approximately +/xe2x88x9250 xcexcm, LED pitch is relatively coarse, and such methods are unsuitable for use in a high precision printer.
The present invention was therefore conceived as a way to solve the above problems by providing a printer in which the positioning of each color image is dramatically improved and movement such as for primary scanning is not required by the light source used for internal image development.
The present invention is a printer having applied as a latent image light source an EL (electroluminescent) pixel array comprising a base layer having at least a light emitting layer, electrode layers on one side of the base layer, and a TFT (thin-film transistor) layer having a circuit part for controlling light emission of the light emitting layer by applying a predetermined voltage between the electrode layers, and a plurality of pixel parts layered to the other side of the base layer and segmenting the base layer, enabling light emission control of the light emitting layer in the base layer by producing a potential difference to the electrode layers independently in each segmented area.
Furthermore, the printer has a photoconductive drum, a charger section for charging the outside of the photoconductive drum, a developer section for developing an electrostatic latent image formed by the charger section, and a pressure-applying member pressed with a specific nip pressure to the outside of the photoconductive drum, characterized by having a transfer section for transporting a transfer medium held to the outside of the photoconductive drum, and transferring an image developed by the developer section; and a fixing section disposed to the transfer medium transportation path downstream of the transfer section for fixing the transferred image.
In the above-noted printer, a developer section is disposed at a specific pitch for each of plural colors, a charger section is disposed upstream of each of these plural developer sections, and during one revolution of the photoconductive drum charging, exposing and developing each image at a specific width unit in the circumferential direction corresponding to said specific pitch are repeatedly performed to combine plural color images on the photoconductive drum, and after which the images are transferred to the transfer medium.
Because the pixel array used as the light source is disposed completely around the drum, the relative positions of the positions of each pixel and the position of the drum surface always match. Therefore, by only controlling the pixels arrayed in a matrix, there is no shifting in the position of plural color images. Moreover, because the pixel array used as the light source is on the entire surface of the drum, it is compatible with all exposure methods, including page exposure, scanning exposure, and slit exposure. It should be noted that in the present invention an image of a specific circumferential width is formed at once, and each time developing one color is completed, an image of the next color is formed for this particular image width. As a result, development of plural colors is accomplished with one drum revolution, and plural color images can be overlaid to the drum.
The overlaid image is then transferred to the transfer medium in the transfer section, fixed in the fusing section, and ejected. As a result, less time is needed to process one image when compared with a conventional multiple revolution method or tandem method.